Scroll apparatus for fluid compression or expansion are typically comprised of two upstanding interfitting involute spirodal wraps which are generated about respective axes. Each respective involute wrap is mounted upon an end plate and has a tip disposed in contact or near-contact with the end plate of the other respective scroll wrap. Each scroll wrap further has flank surfaces which adjoin in moving line contact, or near contact, the flank surfaces of the other respective scroll wrap to form a plurality of moving chambers. Depending upon the relative orbital motion of the scroll wraps, the chambers move from the radial exterior end of the scroll wraps to the radially interior ends of the scroll wraps for fluid compression, or from the radially interior end of the respective scroll wraps for fluid expansion. The scroll wraps, to accomplish the formation of the chambers, are put in relative orbital motion by a drive mechanism which constrains the scrolls to relative non-rotational motion. The general principles of scroll operation are discussed in numerous patents, such as U.S. Pat. No. 801,182.
The scroll wraps themselves may be manufactured either separately from or integrally with the end plate upon which they are disposed. In the first case, the scroll wrap is typically formed into the desired scroll involute shape, and inserted into a corresponding slot formed in the scroll end plate. The scroll wrap may be retained in the slot by epoxy, a separate key producing a friction fit of the wrap within the slot, deformation of the portion of the scroll wrap within the slot, or similar means. Unfortunately, it is difficult to assure the accuracy of scroll members formed according to this method. For example, there are difficulties in ensuring that the scroll wrap remains true to the desired scroll form, that the scroll tip-to-floor height is constant along the length of the scroll wrap, or that the scroll wrap is perpendicular to the scroll end plate at all points. Also, the manufacture of scroll members by such means typically entails a relatively large number of steps, adding to the complexity and cost of the manufacture of the scroll member.
In the second case, the scroll wrap is machined to final form from a forging or casting which has the general shape of the scroll wrap and end plate, or is machined from a solid plate. Typically, one or more rough cuts will be made with a milling machine to define the general shape of the scroll wrap. At least one finishing cut is made with a milling machine to finish each scroll wrap flank and the floor of the scroll wrap. Another finishing milling cut is typically required to machine the scroll wrap tips. Scroll wraps manufactured by machining typically offer greater strength, increased operating life and improved reliability. However, problems often arise related to the dimensions of the scroll wraps, and such scroll wraps have typically been more costly due to the number of necessary time-consuming machining steps. Since the floor of the scroll wrap is typically machined by a different pass and in some cases even by a different cutter than the scroll wrap tip, it is difficult to ensure repeatability of the tip-to-floor height from one scroll member to the next. It is also difficult to ensure that the width between the adjacent scroll wrap flanks is repeated from scroll member to scroll member. Differences in the tip-to-floor height or the scroll wrap width of interleaving scroll members can contribute to fluid leakage from the chambers and losses in operating efficiency.
Therefore it is an object of the present invention to provide a scroll profile cutter which will generate the scroll wrap tip, floor and scroll wrap flank in one cutting pass.
It is a further objective of the present invention to provide a scroll profile cutter which will ensure repeatable scroll wrap height.
It is yet another objective of the present invention to provide a scroll profile cutter which will have a relatively greater useful life and which will lower the cost of scroll wrap manufacture.
It is an objective of the present invention to provide a scroll profile cutter which will be easily and inexpensively implemented.
These and other objectives of the present invention will become apparent in the specification and claims that follow.